School on Physics, Technology and Applications of Accelerator Driven Systems (ADS) November 2007

Transcription

1 School on Physics, Technology and Applications of Accelerator Driven Systems (ADS) November 2007 Engineering Design of the MYRRHA. Part II Didier DE BRUYN Myrrha Project Coordinator Nuclear Research Division SCK CEN BE-2400 Mol (Belgium)

2 MYRRHA Draft 2 Fuel Pins & Fuel Assembly Pre-Design Vitaly Sobolev & Hamid Aït Abderrahim On behalf of MYRRHA team and MYRRHA support Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

3 CONTENTS 1. General approach to fuel design 2. Determination of fuel pellet sizes 3. Cladding sizes 4. Pre-design of a whole fuel pin 5. Pre-design of a fuel assembly 6. Preliminary estimation of the fuel operation parameters 7. Items still under consideration 8. Conclusions Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

4 1. General approach to fuel design (1) Needed input information: core (spectrum, total power, power density or neutron flux); fuel type (oxide, metal, cermet, ); initial fuel enrichment, composition and density; aimed fuel burn-up; coolant type (liquid metal, gas, ); allowed coolant temperature and flow velocity; cladding material; allowed cladding temperature, corrosion; stresses and strains. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

5 1. General approach to fuel design (2) Core parameters choice : Neutron spectrum -> fast k eff -> ~ 0.95 Total power -> ~ 50 MW(th) Fast neutron flux -> ~ cm -2 s -1 (fuel power density -> ~ 1.5 kw cm -3 ) Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

6 1. General approach to fuel design (3) Fuel choice: Fuel type -> oxide -> MOX; Composition and density -> (Pu,U)O 2 of 95 % TD Initial enrichment -> % Pu (PWR) in HM Aimed (peak) burn-up -> ~ 100 MWd/kg ihm Maximum allowed temperature -> 0.9 T m ~ C Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

7 1. General approach to fuel design (4) Fuel choice: Pu isotopic vector: Isotope Content, wt.% 238 Pu 239 Pu 240 Pu 241 Pu 242 Pu however, the MOX is in disagreement with RERTR program? Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

8 1. General approach to fuel design (5) Coolant parameters choice: coolant type -> LBE (T m =124 C) allowed temperatures -> from 200 C up to 450 C allowed flow velocity -> 2 m s -1 however, the lower temperature limit should (may be) increased because of the clad embrittlement problems.. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

9 1. General approach to fuel design (6) Clad material requirements: 1. Keeping the adequate mechanical performances (strength, ductility, swelling, creep) at high doses and operation temperatures. 2. Resistance to corrosion-erosion attack of LBE flow 3. Resistance to cycling stresses caused by the trips and restarts of the proton beam. ferrite-martensitic or austenitic steels? Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

10 1. General approach to fuel design (6) Comparison of austenitic and ferrite-martensitic steels Swelling Oxidation Pb, 550 C, 2 m/s Thickness, µm Optifer IVc EM time, h Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

11 1. General approach to fuel design (7) Embrittlement of Cr-steels Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

12 1. General approach to fuel design (8) Cladding parameters choice: o Material -> T91 MS (oxygen protection) o Allowed temperature -> 500 C (normal operation) 600 C (transients) o Allowed radiation damage -> ~100 dpa o Allowed swelling -> ~ 5 % o Allowed corrosion -> ~ 10 % SS 316 Ti (corrosion protected) is still kept as back-up solution. however, helium induced embrittlement can be a problem Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

13 1. General approach to fuel design (8a) SS 316 Ti (corrosion protected) is still kept as back-up solution. however, helium induced embrittlement can be a problem Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

14 1. General approach to fuel design (9) Main steps in the fuel rod pre-design: Fuel pellet sizes Clad diameter and thickness Fuel column and gas plenum Preliminary design of a whole rod Design test with fuel performance codes Design optimisation Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

15 2. Determination of fuel pellet sizes (1) Pellets without hole to simplify fabrication. Pellet diameter to satisfy the fuel non-melting conditions: π d 2 pellet vmax melt < fuel max = cool + R cool +R clad +R gap +Rpellet T T T 4 q ( ) q vmax ~ 1.5 kw/cm³ to obtain Φ fast ~ cm -2 s -1 Safety margin T fuel max = 0.9 T melt Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

16 2. Determination of fuel pellet sizes (2) Safety margins for fuel temperature %Pu in HM "Melting" temperature ( C) operation region safe limit (T fuel = 0.9 T melt ) solidus liquidus Burnup (MWd kg-1ihm) Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

17 2. Determination of fuel pellet sizes (3) Fuel thermal conductivity degradation 8 7 MOX type fuel, 95%TD Thermal conductivity, W(m K fresh 50 MWd/kg ihm MWd/kg ihm Temperature, C Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

18 2. Determination of fuel pellet sizes (4) Radial thermal resistivity of fuel rod π d q 4 2 pellet v max melt < fuel max = cool + R cool +R clad +R gap +Rpellet T T T ( ) Pellet type Time R cool R clad R gap R pellet q v max T max T cool D pellet max K m/kw K m/kw K m/kw K m/kw kw/cm³ C C mm Solid BOL Solid EOL mm 6.0 mm The chosen pellet : Ø 5.40 x 6.0 mm (q v = 1.5 W/cm -3 ~ q l = 350 W cm -1 ). however, it would be better to use the pellets with the same sizes as in the developed LMFR (SNR, Phenix, ) Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

19 3. Cladding sizes Clad inner diameter: Gap is to avoid or reduce PCMI Gap thickness δ gap should compensate: fuel thermal expansion fuel irradiation induced swelling (~1.6vol.% per 10 MWd kg -1 ihm) Inner clad diameter: d clad = D pellet + δ gap d clad δ gap (radial)= 75 microns and d clad = 5.55 mm have been obtained as the first estimate. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

20 3. Cladding sizes Liner thermal dilatation of MOX, SS 316 and FMS T Linear thermal expansion, L/L_ SS 316 T91 MOX Temperature, C Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

21 3. Cladding sizes δ clad Clad thickness is chosen to withstand: intrinsic thermal expansion stresses pressure of inside gazes pressure of outside coolant inside corrosion attack of fission products outside corrosion attack of LBE coolant fatigue initiated by power changes caused by the proton beam trips and restarts. PCMI > for ASS < (0.4-1)% plastic deformation for FMS? Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

22 3. Cladding sizes 40 Alowable pressure, MPa p max = 0.5 D [ σ ] δ clad inside clad δ clad [ σ ] = { σ / 2.6; /1.5} min uts σ 0. 2 δ clad Clad thickness, mm δ = 0.5 mm obtained as the first estimate (p clad max = 23 MPa). however cladding sizes should still be optimised after determination of T91 properties at representative irradiation conditions. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

23 4. Whole rod pre-design (1) Fuel column length Compact core -> L active zone ~ D active zone Limited axial form factor -> L fuel Neutronic estimates -> L fuel 600 mm Reflector segments Neutronic estimates -> I ref = mm L ref Material -> YSZ Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

24 4. Whole rod pre-design (2) L fuel Gas plenum volume is determined: by the released amount of fission gas (production rate ~ 115 mole m -3 per 10 MWd kg -1 ihm) by the gas temperature in plenum by the cladding mechanical resistance p tot p0 He Tgas R ηfg Bu ρ fuel Vfuel Tgas = + < T ρ V 0 TD fuel plenum p max L plenum Temperature of gas is a critical parameter which is difficult to determine, especially, in the case of a rapid (burst) gas release. L plenum = = 360 mm was chosen Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

25 4. Whole rod pre-design (3) Plenum pressure (MPa) Burnup = 100 MWd kg -1 ihm Tgas = 250 C Tgas = 450 C Tgas = 600 C 0 0% 20% 40% 60% 80% 100% Released FG fraction Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

26 4.Whole rod pre-design (4) Axial schematics Gas plenum Cladding Spring Bottom-cap Lower reflector Fuel pellets Upper reflector Top-cap A typical design of LMFR rod has been adapted to the MYRRHA specific conditions. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

27 4.Whole rod pre-design (5) Table 5. Main geometrical parameters (in mm) of the fuel pins of some fast neutron reactors and of ADS MYRRHA. SPX Phenix SNR-300 BN-600* EFR MYRRHA Diameter Total length upper gas-plenum upper breeder/reflector 300 (0)** active part lower breeder/reflector 300 (300)** lower gas-plenum * experimental fuel rod with the holed pellets; ** special design. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

28 5. Pre-design of a fuel assembly (1) Main steps in the fuel assembly design: 1) Fuel micro-cell (type and pitch) 2) Assembly radial cross-section 3) Assembly axial schematics 4) Preliminary design of a whole assembly 5) Modelling with suitable thermohydraulic and thermomechanical codes 6) Optimisation Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

29 5. Pre-design of a fuel assembly (2) Microcell = fuel rod + coolant + spacer Microcell type hexagon or triangle fuel pellet D rod sub-channel cladding coolant coolant fuel rod l pitch l pitch Pitch (l pitch )? -> heat balance + pressure drop + fuel fraction Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

30 5. Pre-design of a fuel assembly (3) Heat balance pitch = f (Q rod, T < 200 C, v cool < 2 m/s) Q = ρ c T v S sch cool p cool cool cool cool x pitch l 4 pitch π qlrod lfuel 1+ 2 Dclad 2 3 π Dclad ρcool vcool cp cool T cool x pitch > l pitch 8.02 mm Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

31 5. Pre-design of a fuel assembly (4) Pressure drop pitch = f ( p < 2 bar, v cool < 2 m/s) without spacer Pressure drop (MPa) with a spacer (lead=400 mm) 0.05 x pitch Relative pitch x pitch Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

32 5. Pre-design of a fuel assembly (5) Fuel fraction pitch = f (minimum coolant fraction to obtain k eff ~ 0.95) x pitch = > l pitch =8.55 mm was chosen at this stage of the pre-design. however, a large value is preferable for natural circulation build-up in the case of a pump trip. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

33 5. Pre-design of a fuel assembly (6) interior edge corner Radial cross-section design: 82 mm D rod 85.5 mm 1. Edge and corner subchannels optimisation 2. Determination of a number of rods in FA Radial gradient limits. 4. Shroud thickness bowing, deflection? 5. Bundle grids and other elements. 6. Thermohydraulic and thermomechanical modelling 7. Optimisation 8.55 mm Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

34 5. Pre-design of a fuel assembly (7) 1844 input nozzle 1200 mixturer grid fuel rods A typical design of LMFR sub-assembly has been adapted to the MYRRHA specific conditions. however the estimates have been performed only at start conditions. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

35 5. Pre-design of a fuel assembly (8) Main geometrical parameters (in mm) of the hexagonal sub-assemblies of some LMFR and of ADS MYRRHA. SPX Phenix SNR-300 BN-600 EFR(II) MYRRHA Number of pins Pin diameter SA Width Total length Fuel pin length SA Pitch Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

36 6. Preliminary estimations of fuel operation parameters (1) Input from neutronic modelling: Power and flux in the hottest rod Neutron flux (near the hottest rod): total En > 0.75 MeV En > 1 MeV Core thermal power Peak power density (fuel) Average power density (fuel) Radial power form-factor n/cm²s MW kw/cm³ kw/cm³ (max/aver rod) Peak liner power (hottest rod) Average liner power (hottest rod) Axial power form-factor (hottest rod) W/cm W/cm (max/aver) Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

37 6. Preliminary estimations of fuel operation parameters (2) Input from neutronic modelling: Power distribution in the hottest assembly and in the hottest rod Pin power, kw LHGR, W/cm Hottes rod Central rod S Axial co-ordinate, mm Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

38 6. Preliminary estimations of fuel operation parameters (3) Initial axial temperature distribution in the hottest rod T melt = 2685 C 1800 Temperature, C Pellet center Pellet surface Clad outside Coolant Axial co-ordinate, m Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

39 6. Preliminary estimations of fuel operation parameters (4) Initial radial temperature distribution in the hottest rod T melt = 2685 C Temperature, C pellet gap clad Radial co-ordinate, mm Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

40 6. Preliminary estimations of fuel operation parameters (5) Pellet-clad gap at start within the hottest rod 80 Cold gap Radial gap, micron Hot stand-by After start Axial co-ordinate, m Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

41 6. Preliminary estimations of fuel operation parameters (6) Two scenario s for the proton beam operation in a cycle 2.0 Beam current ratio Constant flux scenario 2 scenario Time, d Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

42 6. Preliminary estimations of fuel operation parameters (7) Power history and peak burnup evolution in the hottest rod (constant flux regime) LHGR average Burnup max LHGR average, W/cm Time, d Bu max, MWd/kg ihm Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

43 6. Preliminary estimations of fuel operation parameters (8) Peak temperature evolution in the hottest rod (modelling with MACROS) Fuel centreline temperature, C mean peak melting Time, d Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

44 6. Preliminary estimations of fuel operation parameters (8a) Peak temperature evolution in the hottest rod (modelling with FEMAXI conservative case) 2700 fuel melting limit 2200 Peak temperature, C Time, d Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

45 6. Preliminary estimations of fuel operation parameters (9) Evolution of the mid-plane pellet-clad gap in the hottest rod 100 (modelling with MACROS) 80 Gap, micron Time, d Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

46 6. Preliminary estimations of fuel operation parameters (9a) Evolution of the mid-plane pellet-clad gap in the hottest rod (modelling with FEMAXI conservative case) Radial gap Contact pressure Contact pressure, MPa Radial gap, microns Time, d Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

47 6. Preliminary estimations of fuel operation parameters (10) FGR and pressure build-up in the hottest rod (modelling with MACROS) Pressure FGR 25 Plenum pressure, MPa FGR, % Time, d 0 Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

48 6. Preliminary estimations of fuel operation parameters (10a) FGR and pressure build-up in the hottest rod (modelling with FEMAXI conservative case) 60 Gas pressure average FGR peak pellet FGR 60 Gas pressure, bar FGR, % Time, d 0 Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

49 6. Preliminary estimations of fuel operation parameters (11) Clad oxidation and temperature rise in the hottest rod Oxide thickness, microns Oxide outside (maximum) Oxide outside (average) Clad average temperature, C Clad temperature outside (midplane) Time, d 200 A better protection of the T91 cladding is needed or a lower temperature after 2-3 cycles of operation Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

50 6. Preliminary estimations of fuel operation parameters (12) Pressure drop in assembly (<T> = 300 C, G = 55.5 kg s -1 ) 2 G = 2 ρ ( + ξ ( friction) contr / exp an) i i passembly = pi 2 i i Si flow No. Element p bar % 1 Inlet tube, nozzle, hex-duct Fuel rod bundle (free part) Upper grid Upper hex-duct, matching cone, outlet tube TOTAL 1.6 ξ A more detailed thermal hydraulic modelling of assembly was performed with RELAP5 by SH, but the results at the normal operation have not yet been included in Draft-2 Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

51 6. Preliminary estimations of fuel operation parameters (13) Thermomechanical modelling of assembly (with STRAW by BELGONUCLEAIRE, but old variant from Draft-1) Thermomechanical modelling of assembly has still to be performed. but with which code? Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

52 7. Items still under consideration To fix the fuel Pu enrichment and the Pu isotopic vector. To establish a highly enriched MOX (30% Pu) properties database up to burn-up of 100 MWd/kg ihm. To establish the irradiated cladding properties database (T91 and others). To define realistic core management scenarios (k eff swing compensation with meeting the requested performance). To perform thermomechanical modelling of fuel assembly. To optimise the current designs of fuel rod and fuel assembly. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

53 8. Conclusions (I) Preliminary design of the MYRRHA fuel rod, fuel assembly and core has been updated to meet 50 MW(th) power. Modelling of the thermomechanical behaviour of the fuel rod under conservative (constant flux) irradiation conditions shows that the initial safety margins are sufficient for about three (two) years of the normal operation up to the aimed maximum burnup of ~100 MWd/kg ihm. The clad damage limit of 100 dpa are estimated to be within the achievable range taking into account the clad operating temperature range of C and the moderate He production rate (maximum 8 appm He/dpa). Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

54 8. Conclusions (II) The designed hexagonal fuel assemblies with medium pitch ratio of 1.3 can provide the adequate heat removal at normal operation with the maximum LBE local velocity of 2 m s -1 (and at protected DBC transients?). The following progress in the optimisation of the designs of the fuel pin and the fuel assembly will be made after solving urgent problems existing in the fuel and cladding database properties and redefining a realistic core management scenarios. A validation and qualification programme for fuel is highly recommended to start ASAP, taking into account that at least 2-3 (up to 5) years are needed to fulfil this kind of irradiation programme. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

55 Acknowledgements This presentation was prepared with the contributions of LEMEHOV Sergei, Al MAZOUZI Abderrahim, MALAMBU Edouard, HAECK Wim Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

56 ANNEX Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

57 What we had in DRAFT-1 Only two pages on the fuel pin and assembly design (pp , three figures included) were presented in the Draft-1 Document. Three different fuel designs were analysed: SPX, BN-600 and SNR-300. The existing SPX fuel design (but with HT-9, T91 or AISI 316L cladding) was used as reference in order to keep the shortest pre-design and expected deployment schedules. A high flux of the fast neutrons: ~ n/cm²s in the hottest experimental channels at the initial k eff ~ A small core thermal power - few tens of MW Fuel performance calculations only at start. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

58 Choice of the driver fuel Options: 1. What actinides? enriched U, Pu-U, Pu-Th, U-Th. 2. Enrichment level? how to deal with 20 % U-235 equivalent limit? 3. What chemical form? metal, oxide, carbide, nitride. 4. Physical state? solid solution, mixture, CERMET, (Pu,U)O 2 MOX with 30 wt.% RG Pu in HM has been chosen in MYRRHA, however, it would be useful to revisit other options. Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

59 Cladding choice SS 316 Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

60 Determination of fuel pellet sizes Radial thermal resistivity of fuel rod 1 Tfuel centre R pellet = 1 λ ( ) 4 π pellet λpellet T λ pellet T fuel T < > dt fuel surface 1 R = cool π D h clad h ( ) heat xpitch heat vcool D clad λcool = a p cool Dclad δ clad Rclad π D clad λ clad δ gap Rgap π D gap λ gap Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

61 Determination of fuel pellet sizes Radial thermal resistivity of the holed pellet Hole factor d hole d hole ln 1 D pellet D pellet R pellet = π λpellet d hole 1 D pellet Relative diameter of hole T fuel centre 1 < λpellet > λpellet ( T) dt T fuel T fuel surface Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

62 Determination of fuel pellet sizes Radial thermal resistivity of the coolant boundary layer: v = 2 m/s, <T> = 300 C 3.5E-03 Heat resistance, K/W 3.0E E E-03 D = 6 mm = 7 mm = 8 mm 1.5E E Relative pitch Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

63 Determination of fuel pellet sizes Radial thermal resistivity of 0.5 mm T91 cladding 1.3E E-03 D = 6 mm = 7 mm = 8 mm Heat resistance, K m/w 1.1E E E E E Temperature, C Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October

64 Determination of fuel pellet sizes Radial thermal resistivity of 0.1 mm gap filled with He-gas at 0.5 MPa (STP) 3.0E E-02 D = 6 mm = 7 mm = 8 mm Heat resistance, K m/w 2.0E E E Temperature, C Presented at the Workshop on Technology and Applications of Accelerator Driven Systems, Trieste, October